Office of Homeland Security Director
Tom Ridge said yesterday that the bacterial spores that caused anthrax outbreaks
in Florida, New York and Washington belong to the so-called Ames strain -- a
subtype of the anthrax bacterium that is commonly used in universities around
the world and was a focus of studies by the U.S. military.

Ridge's comments marked the first time
that a government official has specified the strain of bacteria that has been
sent in letters to
Senate Majority Leader Thomas A. Daschle (D-S.D.) and news organizations.

Officials also confirmed that the
spores sent to Daschle in a letter opened in his office Oct. 15 were very small,
highly concentrated and of high quality.

But they would not answer questions
about news reports yesterday that the spores had been treated with a chemical
additive to enhance their volatility and make them more likely to cause serious
disease. They said ongoing tests could take some time to complete.

Experts have said those tests could
narrow the search for the perpetrators of the bio-terrorism attacks.

"We are trying very hard to
characterize anything that would be associated with this sample and we're
continuing to do that research," Maj. Gen. John Parker of the U.S. Army Medical
Research and Materiel Command told reporters at a midday news conference. "And I
won't have the absolute answers until all of those investigations are in."

The Washington Post reported
yesterday that the spores in the Daschle letter had been treated with a chemical
additive using technology so sophisticated that it almost certainly came from
the United States, Iraq or the former Soviet Union. A government official with
direct knowledge of the investigation has said that the totality of the evidence
so far suggests it is unlikely the spores were originally produced in the former
Soviet Union or Iraq.

The letter to Daschle is believed
responsible for five inhalational anthrax infections -- two of them fatal (case
14 and case 15) --
in the Washington area, though authorities have not ruled out the possibility
that there are other undetected letters carrying anthrax microbes.

Ridge said the spores inside the letter
sent to Daschle had "some different characteristics" when compared to the spores
found in letters sent to NBC News in New York and the New York Post. The
letters to the media organizations were postmarked Sept. 18 in Trenton, N.J. The
Daschle letter was postmarked Oct. 9 in the same location.

"It is highly concentrated," said
Ridge. "It is pure and the spores are smaller. Therefore they're more dangerous,
because they can be more easily absorbed in a person's respiratory system." By
contrast, the contents of the New York Post letter were clumpy, he said.

It was not immediately clear whether
those differences were significant or whether the New York Post sample
had simply become sticky from having become damp while in transit.

In other regards, the spores found in
all three letters -- as well as those suspected to have caused the Oct. 5 death
of a tabloid newspaper photo editor (case
5) in Boca Raton, Fla. -- are indistinguishable, Ridge repeated yesterday.
Specifically, he revealed yesterday, they belong to the Ames strain.

That strain was first isolated in Ames,
Iowa, and sent in 1980 to Army researchers, who have since distributed it to
various academic laboratories.

The strain has spread by other routes
to countless research labs around the world, making its identification
relatively useless as a tool for tracking the perpetrators, experts have said.

Also yesterday, officials said that
investigators in New Jersey have been disappointed to find no evidence of
anthrax along the West Trenton postal route of mail carrier
Teresa Heller (case
4), whose positive test for the cutaneous form of disease had been seen as a
possible lead in the case.

More than 20 tests conducted at the
West Trenton post office and in mailboxes and bins along her route turned up
negative, FBI officials said, leading them to focus their inquiries on a
distribution center in Hamilton Township that feeds into West Trenton.

That facility processed at least three
letters containing anthrax spores, and 13 sites out of 23 tested in the building
showed signs of anthrax bacteria.